Abstract: Exosomes are membranous vesicles that are actively secreted by cells. They can be isolated from various cell culture media and animal body fluids. Exosomes are mainly composed of lipids, proteins and nucleic acids. They have small molecular structure and high biocompatibility with size of 40-100 nm. In addition, exosomes are natural endogenous nanocarriers that can transport lipids, proteins, DNA and RNA. Studies have shown that exosomes play an important role in long-distance communication between cells, in physiological and pathological processes. This article introduces the composition and physiological functions of exosomes, and summarizes the relevant content of exosomes as drug delivery vehicles. The applications of exosomes in central nervous system diseases, especially brain diseases and tumors are summarized.